Small fluorescent grow lamps don’t generate as much heat as incandescent lamps, so you can situate them much closer to your plants, especially young seedlings, for better results.

In a fluorescent fixture that holds four to eight tubes, you can use a combination of lamps with different color spectrums. If you buy a T5 fixture that holds eight fluorescent tubes and is zoned with multiple on and off switches, you can turn on only your blue lamps during the vegetative phase and then switch on the red with the blue to initiate flowering.

Gardening Under Lights Book

If you are looking to boost flower production, HPS lamps traditionally outperform both MH and fluorescent lamps. In terms of total light output, an HPS lamp will provide about six times the light of an incandescent lamp.

Because HPS lamps produce a warmer spectrum of light, they are often used to trigger flowering in plant crops.

Gardening Under Lights Book

If you are growing just a few plants in a very small space, CFLs produce a good spectrum for cannabis and can be placed much closer to your plants than HID lamps. HO T5 fluorescents are also a good option. Both are best suited to growing plants during their vegetative phase, so you might consider supplementing with some red light during the flowering phase with warm-spectrum T5s or red LEDs.

HID LED rigs are good for both growth phases of cannabis. You will need to place HID LED fixtures a bit further away from your plants than you would CFLs or T5 fluorescents.

If you are growing larger groups of cannabis plants, you'll be better served by upgrading to HID lighting (Metal Halide, High-Pressure Sodium, CMH/LEC, or HID LEDs) for best results.

New BOOK! Gardening Under Lights: The Complete Guide for Indoor Growers

I use my quantum flux meter to make decisions about which lamps I’ll use to grow which plants, and at different stages of development.

Don’t confuse a quantum flux meter with standard visual light meters or Watt meters. Using a Watt meter and a standard light meter that measures lumens, you can calculate LPW outputs for a given lamp, which helps you assess efficiency.

You can also use standard light meters to measure footcandles of light. But remember that standard light meters, which measure in footcandles or lux, are not accurate for determining plant light needs.

Gardening Under Lights Book

If you’re growing fruiting crops, you can switch plants or lamps to a warmer spectrum (more red light) once you’ve bumped them up to larger pots to trigger stem elongation and flowering. If you need your plants to flower and they require a specific photoperiod to do so, they will require red light.

Cannabis will need close monitoring of lighting to trigger the plants into flowering.

Gardening Under Lights Book

CMH lamps offer a solid full-spectrum output, including some UV and far red light. They are available in two Kelvin measurements: 3100K and 4200K. The 3100K lamps are good for growing plants from vegetative to flowering to fruit without switching lamps, whereas 4200K lamps are best for propagation and vegetative growth.

Fruiting crops like cucumbers, squash, peppers, and tomatoes flower very well under a 315-watt 3100K LEC (Light Emitting Ceramic) lamp without any additional red-light sources.

Gardening Under Lights Book

Peas are one of the oldest cultivated vegetables (although botanically the pods are a fruit and the peas are seeds). Peas are a very versatile crop you can grow peas for the fresh green seeds, the green pods, foliage, young shoots for sprouts and microgreens, and dried seeds.

Peas grow best between temperatures of 50°F and 70°F (10– 21°C). They can tolerate warmer temperatures, but you will need to water more frequently. If you're growing peas indoors, stick to cooler parts of your home and grow lamps that emit less heat.

New BOOK! Gardening Under Lights: The Complete Guide for Indoor Growers

Cannabis grows in two phases. During the vegetative phase you light plants for 18 to 24 hours to inhibit flowering and put on vegetative growth.

If you don’t have a lot of space and cannot accommodate large plants, you’ll veg your plants for three to four weeks, then shift them to a flowering phase with alternating 12-hour cycles of light and dark (or the specific critical daylength required by your strain) to induce flowering.